Smartphone App Boosts Bystander Response to Cardiac Arrest

When citizen responders arrived before EMS, it increased the likelihood of bystander CPR and defibrillation. An RCT is ongoing.

Smartphone App Boosts Bystander Response to Cardiac Arrest

A smartphone app that sends citizen volunteers running to the scene of out-of-hospital cardiac arrests, even to people’s homes, holds the potential to increase rates of bystander CPR and use of automated external defibrillators (AEDs), an observational pilot study conducted in Copenhagen, Denmark, shows.

When citizen responders arrived before emergency medical services (EMS) personnel, it increased the likelihood of bystander CPR (85.3% vs 76.8%; OR 1.76; 95% CI 1.07-2.91) and defibrillation (21.2% vs 6.7%; OR 3.73; 95% CI 2.04-6.84) compared with times when EMS arrived first, according to a study published online ahead of the July 7, 2020, issue of the Journal of the American College of Cardiology.

What’s not yet clear is whether these gains will also translate into lives saved.

“This was bystander interventions from both ‘random’ bystanders and citizen responders, but we found that citizen responders provided CPR in 69%, applied an AED in 50%, and defibrillated in 10% of all cases when they arrived before EMS,” lead author Linn Andelius, MD (Copenhagen Emergency Medical Services, University of Copenhagen, Denmark), told TCTMD in an email.

“Importantly, these numbers were increasing with increasing EMS response times,” she added. “We did not know how many minutes before EMS they arrived, but this shows that citizen responders have the potential to increase bystander interventions and might have a bigger influence when EMS response times are long.”

Thirty-day survival was not significantly different based on whether citizen responders arrived before or after EMS, but Andelius said the potential to improve patient outcomes using this approach is there. “I do think so, but I think it is very important to evaluate this in a correct way since right now over 80,000 citizen responders are registered in Denmark and we have to know that app dispatch actually improves survival for out-of-hospital cardiac arrest patients,” she said. “Otherwise we cannot ask citizen responders to devote their time and expose them to the potential risk of physical or psychological injury.”

The ongoing HeartRunner trial, with the aim to randomize 1,600 patients, will more definitively explore the impact on 30-day survival.

The Heartrunner App

Andelius noted that in Denmark, rates of bystander CPR have increased dramatically in recent years, from 37% in 2008 to 77% in 2018, with the rate of bystander defibrillation remaining low at around 4% before introduction of the Heartrunner app.

Activating citizens near the site of a cardiac arrest through text messages or smartphone apps has the potential to increase bystander interventions, so Copenhagen EMS and the Danish foundation Trygfonden teamed up to introduce the Heartrunner app, which was developed in Sweden, to the Capital Region of Denmark, home to about 1.8 million people.

The region is served by a single emergency dispatch center, which activates nearby citizen responders through the app at the same time as EMS personnel when a call for a suspected cardiac arrest comes in. Some responders are sent directly to the scene and others are sent to retrieve an AED to bring to the site of the arrest; the app links to a nationwide network mapping all voluntarily registered AEDs with information about location and accessibility.

By the start of the study period, 1,030 adult Danes had registered in the app, with another 22,087 signing on over the next year. The median age at registration was 34 years; 50.7% of the volunteers were men, 26.0% were healthcare professionals, and 98.6% said they had received CPR training.

For this study, a pilot for the randomized HeartRunner trial, the researchers compared what happened when at least one citizen responder arrived before EMS with instances when EMS arrived first during the first year of implementation. Of 438 confirmed cardiac arrests, citizen responders got there first in 42% of cases, a number that is increasing as more people sign up for the app, Andelius said.

When citizens arrived before EMS, the odds of bystander CPR and defibrillation went up, reaching rates of 85.3% and 21.2%, respectively. To put those numbers into context, rates were 77.5% and 9.3%, respectively, across Denmark in 2018.

The investigators also assessed the safety of the app-based strategy, finding that only one of the citizen responders reported a physical injury requiring hospital treatment (a lower-extremity fracture sustained while running to the site of the arrest). Three other volunteers reported minor injuries that didn’t require treatment and another three said they were at risk of physical injury or were injured. Of those responding to a question about psychological impact, 1.4% said they were impacted severely, including three who needed professional follow-up. Even so, 99.0% of survey respondents wished to continue with the program after being dispatched.

“Very few citizen responders report physical injury or severe psychological distress after they are dispatched,” Andelius said. “We debrief all citizen responders who report severe distress and they can always contact us for debriefing. These are two important aspects that need to be investigated when implementing a citizen responder program.”

Unique Features

Sumeet Chugh, MD (Smidt Heart Institute, Cedars-Sinai Health System, Los Angeles, CA), who co-authored an accompanying editorial, told TCTMD that even though there are other apps geared toward increasing bystander CPR in cases of out-of-hospital cardiac arrest, the Heartrunner app has some features that make it stand out.

For one, it enables ongoing communication among all the players involved—the dispatcher, the citizen responder, and the caller. That allows, for instance, for the dispatcher to tell the caller that someone will be coming to initiate CPR, an aspect that facilitates bystander response in people’s homes. In this study, 79.9% of events that saw citizen responders arrive before EMS occurred in residential locations. And second, Chugh pointed out, the app dispatches some responders directly to the scene and some to retrieve an AED first.

“Those are two simple but very innovative aspects of this app that make it much easier and user- friendly,” he said.

Asked whether this approach could be applied in other types of settings, Chugh indicated that that remains to be seen. He noted that in the Capital Region of Denmark, the level of bystander CPR education is very high. Indeed, Andelius explained that in Denmark CPR education is mandatory in primary school and when acquiring a driver’s license, and that many workplaces also provide education.

For those reasons, randomized trials testing the app-based approach, like the HeartRunner trial, are needed, Chugh said. “If this clinical trial proves to be positive, especially if survival benefits are seen, then I think this kind of trial should be done in other settings as well,” he said. “That would be a useful thing to do before we deploy it in other settings.”

Andelius acknowledged that a challenge with this approach “is going to be to keep citizen responders engaged since they receive alarms so rarely and might forget about the app. This can be helped by feedback about their work and success stories.”

Moving forward, she added, “we should investigate different app adjustments such as the number of citizen responders who are dispatched, the most optimal radius of activation, the effect in urban versus rural areas, and, in the longer run, cost-effectiveness for citizen responder programs.”

Todd Neale is the Associate News Editor for TCTMD and a Senior Medical Journalist. He got his start in journalism at …

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  • The citizen responder program in Denmark is financially supported by the Danish foundation, TrygFonden, which also funded this study.
  • Andelius reports having received research grants from TrygFonden.
  • The editorial was funded by grants from the US National Heart, Lung, and Blood Institute to Chugh.